The vast majority of youth in foster care have been exposed early in life to overt physical abuse, sexual abuse, chronic neglect, parental substance abuse and/or have been witnesses to interpersonal violence. These exposures can result in extremely disordered or disorganized attachments with early caregivers, which can greatly impact how they relate to others later in life including sexual partners, health care providers, and important adult mentors. These troubled relationships all have been shown to impact risk of sexually transmitted infections including Human Immunodeficiency Virus (HIV/STI). Indeed, adolescents in the foster care system are at between 2-14 times increased risk of sexually transmitted infections compared with youth in the general population. The candidate's long-term objective is to develop an enhanced behavioral intervention to reduce HIV/STI tailored to the needs of adolescents in foster care. Intervention development will be guided by adult attachment theory and specifically by an understanding of how attachment style (e.g., having an avoidant, anxious or secure style) can impact romantic/sexual, health care, and mentoring relationships and consequently can impact HIV/STI risk. To achieve this objective, the candidate will pursue didactic and experiential training to improve knowledge and skills in three specific areas: 1) techniques to assess mediational relationships commonly used in behavioral HIV/STI research, 2) application of adult attachment theory including the use of this theory to improve HIV/STI prevention efforts among adolescents in foster care, and 3) techniques in community-based intervention development that are relevant to HIV/STI prevention research in adolescents with histories of early adverse exposures. The candidate has identified two mentors with complementary expertise in HIV/STI research (Dr. Jane Simoni) and research involving youth in the child welfare system (Dr. Mark Courtney). Additional mentoring will be provided by consultants with expertise in mediational analysis techniques, adult attachment theory, community-based research, bioethics, and biostatistics, and will also include a national expert on community-based HIV/STI research in high-risk adolescent populations (Dr. Ralph DiClemente). The three inter-related studies proposed in this application build on the candidate's training goals and will each contribute to an improved understanding of how adult attachment theory can be applied to develop an enhanced intervention that involves the promotion of healthy relationships to reduce HIV/STI risk among adolescents in the foster care system. The specific aims are to: 1.) conduct a quantitative analysis using an existing longitudinal dataset to understand how relationship factors (e.g., influences of attachments with romantic partners, health care providers, and non-parental adult role-models) mediate the association between attachment style and sexual risk for youth in foster care; 2.) use qualitative methods to elucidate the factors that can directly promote healthy sexuality and HIV/STI-protective behaviors among foster youth in foster care with different attachment styles; and 3.) develop and pilot an enhanced HIV/STI intervention for youth in foster care that includes components that utilize an understanding of adult attachment style to promote healthy romantic/sexual relationships, health care and mentoring relationships. The excellent research environments provided by both Seattle Children's Hospital Research Institute and the University of Washington, as well as the candidate's strong existing relationships with two community partners - the YMCA of Greater Seattle's Center for Young Adults and the Washington State Department of Health and Social Services agency - will enhance the candidate's training and facilitate project goals. After obtaining training, experience, and skills through this K23 Award, the candidate will be prepared to pursue funding to conduct a larger randomized controlled trial of an intervention to reduce HIV/STI risk among youth in the foster care system.